Conventionally, for example, liquid raw material vaporization supply apparatuses for supplying raw material fluids have been used for semiconductor manufacturing devices, in which the metal organic chemical vapor deposition (MOCVD) is used (for example patent documents 1 to 4).
This kind of liquid raw material vaporization supply apparatus, for example, as shown in FIG. 8, stores a liquid raw material L such as TEOS (Tetraethyl orthosilicate) in a liquid storage tank 100, supplies a pressurized inert gas FG to the liquid storage tank 100, pushes out the liquid raw material L in the liquid storage tank 100 with a constant pressure by the pressurized inert gas FG and supplies to a vaporizer 101, heats the liquid raw material L in the vaporizer 101 by a heating means 102 such as a jacket heater to vaporize the liquid raw material L, controls the vaporized gas to have a predetermined flow rate by a flow-rate control device 103 and supplies the gas to a semiconductor manufacturing device 104. In FIG. 8, a numeral 110 represents a stop valve, and a numeral 111 represents a vacuum pump.
In order to replenish a reduced liquid raw material L in the vaporizer 101 due to the vaporization of the liquid raw material L in the vaporizer 101, it is necessary to detect a reduction in the liquid raw material L and replenish the reduced portion to the vaporizer 101.
Conventionally, for detecting the reduction in the liquid raw material in the vaporizer 101 and replenish the same, a control valve 105, which controls the supply of the liquid raw material L to the vaporizer 101, is provided in a supply channel 106 to the vaporizer 101, a pressure detector 108 is disposed to detect the pressure of the gas in a gas passage 107 communicating with the vaporizer 101 and the flow-rate control device 103, and the control sequence including the following steps has been repeatedly performed: monitoring the gas pressure in the vaporizer 101 by the pressure detector 108, when the detection pressure of the pressure detector 101 becomes a predetermined value or lower because the liquid raw material L in the vaporizer 101 is vaporized and reduced in an amount, opening the control valve 105 for a predetermined time, then closing the control valve 105 to supply a predetermined amount of the liquid raw material into the vaporizer 101. When the liquid raw material L in the vaporizer 101 is again vaporized and decreased so that the detected pressure reaches the predetermined value, opening the control valve 105 for a certain period of time and then closing the same.